Epidemiologic Trends in Maxillofacial Trauma Surgery in Germany—Insights from the National DRG Database 2005–2022

Background: Maxillofacial trauma (MFT) caused by falls, interpersonal violence or traffic accidents leading to fractures of different facial regions, including the midface and the mandible, are common clinical conditions requiring open reduction and internal fixation. The aim of this study was to analyze the incidence and time trends in MFT-associated surgeries regarding different facial regions in the German healthcare system over time. Materials and methods: Nationwide data regarding the national diagnosis-related group (DRG) inpatient billing system was received from the German Federal Statistical Office for the years 2005–2022. We estimated the age–gender standardized incidence of MFT-associated procedures classified by the Operation and Procedure Classification System (OPS) and evaluated age- and gender-adjusted time trends using Poisson regression analysis. Results: The total standardized incidence rate of MFT-associated procedures in the observational period 2005–2022 was 25.1 (♀13.3; ♂37.5) per 100,000 person-years within a slight significant annual decrease of 0.5%. A significant increase in the incidence of MFT-related procedures within the observational period was found in older adults from 60 to 79 years (+55.1%; ♀+54.8%; ♂+56.3%) and elderly patients over 80 years (+66.7%; ♀+59.1%; ♂+85.1%). Other significant trends are decreases in MFT-related procedures performed in children from 0–14 years (−28.1%; ♀−30.3%; ♂−27.3%) and young adults between 15 and 35 years (−20.4%; ♀−7.3%; ♂−22.5%). Conclusions: MFT-associated surgery is a persisting challenge in the German healthcare system. There is an ongoing transition in MFT-associated surgeries from younger to older patients beyond the scope of demographic change, highlighting the increasing importance of interdisciplinary treatment of patients with pre-existing conditions in maxillofacial surgery. Implementation of injury prevention measures might be beneficial in this population.


Introduction
Maxillofacial fractures represent a significant category of bone fractures, with a substantial impact on healthcare, quality of life and a considerable economic burden [1][2][3][4].Maxillofacial fractures encompass a range of injuries affecting the mandible, the maxilla, the zygomatic complex, the orbital walls, the teeth, and the paranasal and frontal sinuses.A significant proportion of patients in maxillofacial departments in Germany are those with maxillofacial trauma (MFT) [1].It is notable that traumatic facial injuries are particularly prevalent among young adult males [5,6].The most common causes are physical violence, road traffic accidents, falls and sports and leisure injuries.Such occurrences are subject to pronounced seasonal trends and fluctuations [1, 7,8].The standard procedure for fractures of most facial regions is open reduction and internal fixation [9,10].Despite the growing evidence supporting the superiority of surgical treatment for mandibular condylar process fractures over the past two decades, conservative treatment with closed reduction and maxillomandibular fixation remains a viable option [11].Virtual image segmentation, CAD/CAM planning, navigated surgery, additively manufactured patient-specific implants, and intraoperative three-dimensional imaging have significantly expanded the possibilities of surgical treatments in all areas of facial traumatology by personalizing surgical therapy.This may lead to improvements in the predictability of surgical methods and improved functional and aesthetic outcomes, as well as an extension of the range of indications for open surgical versus conservative treatment options [12].
Historically, in the era of early industrialization, the incidence of maxillofacial fractures increased due to occupational accidents, leading to improvements in occupational safety.With the development of individual mobility, maxillofacial fractures caused by traffic accidents increased significantly until the introduction of airbags and mandatory seat belts in cars.Conversely, sports and leisure accidents, as well as fractures caused by physical violence, have increased in recent decades [13,14].There is only scarce data on the incidence and time trends of maxillofacial fractures in Germany in recent years.Data from a regional single-center study suggest a slight overall increase in midfacial fractures, with a strong increase among elderly people and a slight decrease in midfacial fractures among younger people [6].Nevertheless, there is a paucity of population-based data concerning trends in the incidence of maxillofacial fractures.Studies from other industrialized countries remain indistinctive.Some studies suggest an increasing incidence of MFT-associated fractures [15][16][17].Others show a decrease in the number of facial fractures [18][19][20].To the best of our knowledge, there is no nationwide investigation representing a Central European country like Germany.The objective of this study was, therefore, to estimate the national and regional age-and gender-standardized incidence of MFT-associated procedures in Germany between 2005 and 2022 and evaluate age-and gender-adjusted time trends.

Materials and Methods
The national diagnosis-related groups (DRG) inpatient billing system encompasses data from all German hospitals that use the DRG system.The DRG system covers more than 99% of inpatient treatments in Germany.Hospitals are legally obliged to furnish comprehensive data concerning the care provided, including patient demographics, diagnoses, comorbidities, complications, and procedures.Surgical procedures performed between 2005 and 2022 were classified according to the OPS (Operation and Procedure Classification System), a German modification of the ICPM (International Classification of Medical Procedures).All diagnoses were coded in accordance with the ICD-10GM (German version of the International Classification of Diseases and Related Health Problems, 10th Edition).A comprehensive account of all surgical procedures pertaining to open reduction and internal fixation, classified according to the OPS (coded 5-760, 5-761, 5-762, 5-763, 5-764, 5-765, 5-766 and 5-767) were provided by the German Federal Statistical Office (Statistisches Bundesamt-Destatis.Genesis-Online.Data license by-2-0).The OPS classification of the surgical procedures distinguishes between 5-760 fractures of the lateral midface, including zygomatic bone and zygomatic arch fractures, 5-761 fractures of the central midface, including fractures at Le Fort I and Le Fort II levels, 5-762 fractures of the central and lateral upper midface including fractures at Le Fort III Level and nasoorbitoethmoidal fractures, 5-763 combined and complex midfacial fractures, 5-764 mandibular body fractures, 5-765 fractures of the mandibular ramus and the condylar process, 5-766 orbital wall fractures and 5-767 frontal sinus fractures.The dataset comprises all inpatient procedures pertaining to maxillofacial fractures conducted in Germany over the specified observational period, classified by year, gender, age, and federal state.The number of MFT-associated procedures per year (PPY) was calculated and reported.The mean age of patients was calculated.The normality of the distribution of continuous variables was evaluated using the Kolmogorov-Smirnov test.Continuous variables with a normal distribution were presented as the mean and standard deviation.The means of two continuous, normally distributed variables were compared using an independent sample Student's t-test.A p-value of less than 0.05 was considered to indicate a statistically significant difference.Furthermore, population-adjusted rates of MFT-associated procedures per 100,000 personyears were calculated using population data provided by the German Federal Statistical Office and reported with a 95% confidence interval.To eliminate the potential impact of seasonal variations, the analysis of MFT-associated procedures was conducted on an annual basis.
The primary analysis was conducted on the entire population, with subsequent analyses stratified by gender, age group, affected facial region, and federal state.We calculated the crude and age-sex standardized incidence rates of MFT-associated procedures for each calendar year using the German population from the latest census (2011) as the standard population.To exclude bias due to demographic heterogeneity over time, we divided the population into five age classes: 0-14, 15-34, 35-59, 60-79, and ≥80 years.To ascertain male and female incidence rates, age standardization was performed with the aforementioned age classes using the age distribution of the male and female standard population, resulting in different weights for both genders.The 95% confidence intervals (95% CI) of the crude and standardized incidences were calculated using the delta method.Separate Poisson regression models were constructed to investigate time trends, fitted with incidence rates of MFT-associated procedures as dependent variables and age group, gender, facial region, federal state and year starting from baseline year 2005 as independent variables.The age group of 35-59 years and the female sex were used as a reference group.All models were adapted through a descale adjustment to account for the overdispersion of the outcome variable.The statistical analysis was performed using IBM SPSS Statistics Version 29.0 (IBM Deutschland GmbH, Böblingen, Germany).

Results
A total of 374,143 MFT-associated procedures were registered in Germany between 2005 and 2022 and were thus included in the study.The distribution of age, gender, facial region, and year of treatment for MFT is presented in Figure 1 and Table 1.
The majority of procedures were performed on patients aged 35 years or older (59.5%) and male (72.9%).The mean age exhibited an increase over the course of the study period, from 41.6 years between 2005 and 2013 to 46.3 years between 2014 and 2022 (p < 0.01).The most common fractures necessitating surgical intervention were orbital wall fractures (n = 117,666; 31.5%)followed by lateral midfacial fractures (viz.fractures of the zygomatic complex) (n = 102,491; 27.4%) and mandibular body fractures (n = 66,717; 17.8%).The mean age was highest for combined and complex midfacial fractures at 49.0 years and the lowest for mandibular body fractures at 37.3 years.The age-and gender-standardized incidence rates of procedures associated with MFT are presented in Tables 2 and 3 and Figures 2-4 for the total population and stratified by gender, age and procedure.
The overall standardized incidence rate of MFT-associated procedures during the observational period 2005 to 2022 was 25.1 per 100,000 person-years [95% CI: 25.0-25.2],with a range from 22.0 [21.7-22.3] in 2021 to 26.9 [26.5-27.2] in 2012.There was a slight shift in the gender distribution from 75.1% in males and 24.9% in females in 2005 to 70.7% and 29.3% in 2022, respectively.In males, the overall incidence was 37.5 [37.4-37.7],spreading from 31.9 [31.3-32.4] in 2005 to 40.8 [40.1-41.4] in 2009.In females, the total incidence rate was 13.3 [13.3-13.4],varying between 12.1 [11.7-12.4] in 2005 and 14.3 [13.9-14.6] in 2022.Among the different age groups, children from 0 to 14 years had the lowest incidence rates, with a total of 3.6 [3.5-3.7]The majority of procedures were performed on patients aged 35 years or older (59.5%) and male (72.9%).The mean age exhibited an increase over the course of the study period, from 41.6 years between 2005 and 2013 to 46.3 years between 2014 and 2022 (p < 0.01).The most common fractures necessitating surgical intervention were orbital wall fractures (n = 117,666; 31.5%)followed by lateral midfacial fractures (viz.fractures of the zygomatic complex) (n = 102,491; 27.4%) and mandibular body fractures (n = 66,717; 17.8%).The mean age was highest for combined and complex midfacial fractures at 49.0 years and the lowest for mandibular body fractures at 37.3 years.The age-and gender-standardized incidence rates of procedures associated with MFT are presented in Tables 2 and 3 and Figures 2-4 for the total population and stratified by gender, age and procedure.

Discussion
The field of traumatology represents a persistently evolving challenge across numerous medical specialties.Therefore, MFT remains a primary area of interest in oral and maxillofacial surgery.As the most common causes of MFT, such as physical violence, traffic accidents, falls, sports and leisure injuries, remain prevalent, MFT remains an important cause of hospitalization in oral and maxillofacial surgery departments [1].baseline incidence, represents the most declining subgroup for MFT-associated procedures in absolute numbers.
This may indicate that during the observational period from 2005 to 2022, the reduction of interpersonal violence was one of the main reasons for the reduced incidence of maxillofacial fractures.This hypothesis is also supported by the lack of a decline of MFT-associated procedures in women and the rather moderate decline of MFT-associated procedures in women of the same age, for whom physical violence is not the most prominent cause of facial fractures and the shift to a more balanced gender ratio [1,26].Matching this, Kraft et al. showed a reduction in interpersonal violence associated facial fractures and injuries in the recent decades in a regional study in Austria [34].As alcohol consumption is known to be a main risk factor for interpersonal violence-associated facial fractures, the overall reduction of alcohol consumption in Germany within the observational period might be beneficial [1,35].However, there are several studies describing a higher proportion of interpersonal violence in the incidence of facial injuries in different industrialized European and non-European countries, highlighting the strong cultural and regional influences and differences [17,[36][37][38][39]. Road traffic accidents are the second most common cause of facial fractures.The decline in road traffic accidents involving personal injury as a result of the almost complete implementation of airbags and safety belts in recent decades to a historic minimum is a second mechanism explaining a decline in facial fractures, especially among younger persons in Germany [40].The use of protective clothing and helmets in road traffic reached an all-time high during our observational period [41].This conclusion regarding the influence of road traffic accidents is a common observation across the literature and supported by data from a lot of European and non-European countries over the last decades [17,[36][37][38][39].In elderly people, falls are the most common cause of facial fractures, which are insignificant in other age groups [26].The increase in fall-associated facial trauma is a known effect from different studies in several countries with an aging society [15,31,42,43].The significant increase in facial fractures in the age group over 60 years and the increase in average age suggest a significant increase in falls that seems to go beyond the effects of demographic change.Possible reasons for this include an increasingly active lifestyle of elderly people despite the progressive development of neuromuscular and cognitive deficits, including balance and gait disorders, medication side effects and cardiovascular risk factors [44][45][46][47].Another influencing factor may be the trend to smaller family units with an increasing risk of social isolation of elderly people and their lack of social support [48,49].
This study is subject to certain strengths and limitations, which are mainly related to the dataset that was available for analysis.Firstly, it should be noted that the specific reimbursed OPS codes from the national DRG system database only represent MFT treated by open reduction and internal fixation in the analyzed years.The dataset does not include MFT treated non-surgically.Secondly, the study encompasses only those MFT cases necessitating hospital admission and resulting in the billing of a DRG.Patients treated as outpatients or utilizing alternative reimbursement schemes were not included.This could lead to certain groups being underrepresented, for example, older people who are more reluctant to undergo surgery due to pre-existing health conditions.Although the evidence for the superiority of surgical treatment in the area of mandibular condylar process fractures has been proven in the last two decades, conservative treatment with closed reduction and maxillomandibular fixation still plays a certain role and might not be fully covered with the described methods [11].In this context, an increase in surgical interventions for mandibular condylar fractures should not be misinterpreted uncritically as an increase in the underlying fracture frequency.Given that statutory health insurance in Germany offers comprehensive and affordable healthcare coverage to all citizens, and given that MFT is a serious condition that typically necessitates immediate medical attention and hospitalization, it seems reasonable to assume that the vast majority of the German population can be covered and that a comprehensive overview can be provided.The potential of selection bias in MFT determination due to socioeconomic status is mitigated by the population-based approach.The comprehensiveness of our description is constrained by the limitations of the dataset itself, which provides information at an aggregated level and in limited detail, lacking information about the specific cause and severity of the trauma.Consequently, a more advanced analysis, including anamnestic and diagnostic information, was not feasible.Nevertheless, further evaluation of the reasons for the changing incidence of MFT would be of interest.In addition, the DRG inpatient billing database represents an invaluable resource for German researchers engaged in large-scale clinical epidemiology investigations pertaining to procedures and diseases.Furthermore, the utilization of claims data mitigated the potential for recall bias and misclassification bias, which could otherwise arise in studies based on self-reported data.To the best of our knowledge, this study represents the inaugural examination of the time trend of the incidence and epidemiological distribution of MFT-associated procedures at a national level in Germany since the introduction of the DRG system in 2005.The findings may inform an analysis of the influence of population structure and associated factors on the occurrence and treatment of MFT.
The delineation of both beneficial and adverse effects may inform the future identification of risk groups that may profit from social support.To this end, further investigation of the direct influence of social background should be expanded.

Conclusions
Our study suggests that the incidence rate of MFT-associated procedures in Germany has decreased slightly in recent decades, with two main trends running in parallel.There is a sharp decline in MFT-associated procedures in adolescents and young adults.This is accompanied by a strong increase in MFT-associated procedures in older adults over the age of 60, which is also the fastest-growing age group in an aging society.As these two trends are not limited to specific regions or genders, MFT-associated surgeries are a persistent challenge in countries with comprehensive healthcare, such as Germany.There is a continuous transition from younger to older patients in MFT-associated surgery, exceeding the expectations of demographic change, emphasizing the increasing importance of interdisciplinary treatment of patients with pre-existing conditions in oral and maxillofacial surgery.The implementation of injury prevention strategies, including exercise, active needs-based medication management, regular eye examinations and the adoption of safety precautions in the home environment, coupled with the reduction of potential hazards such as steps or stairs, could prove beneficial for elderly patient groups, especially super octogenarians.

Figure 1 .
Figure 1.(a) Age-gender diagram of the total number of MFT-associated procedures 2005-2022.(b) Age-gender diagram of the German population based on census 2011.

Figure 1 .
Figure 1.(a) Age-gender diagram of the total number of MFT-associated procedures 2005-2022.(b) Age-gender diagram of the German population based on census 2011.

Figure 4 .
Figure 4. Standardized procedure-specific incidence of MFT-associated procedures, Germany, 2005-2022.* Significant decrease (p-value time trend Poisson Regression model < 0.05); • Significant increase (p-value time trend Poisson Regression model < 0.05).Reviewing the 16 German federal states individually, the overall incidence of surgical procedures associated with MFT within the observational period ranged from 20.3 [20.0-20.6]per 100,000 person-years in Rhineland-Palatinate to 57.5 [56.1-58.9] in Bremen as shown in Table 4.A single-year minimum was seen in Rhineland-Palatinate in 2006 with 14.7 [13.5-15.9].A single-year maximum was registered in Bremen with 70.4 [64.0-76.8] in 2008.The results

Table 1 .
Total numbers of MFT-associated procedures in Germany 2005-2022.

Table 2 .
Incidence of MFT-associated procedures in Germany 2005-2022.Incidence rates (95% confidence interval) per 100,000 person-years were standardized for the German population based on the Census 2011.Relative Risk (95% confidence interval).

Table 5 .
Results of the Poisson regression models for the total population and stratified by gender, fracture localization and age group.(Germany, 2005-2022).Relative risk for MFT-associated procedure (95% Confidence interval).

Table 5 .
Results of the Poisson regression models for the total population and stratified by gender, fracture localization and age group.(Germany,2005(Germany,-2022)).Relative risk for MFT-associated procedure (95% Confidence interval).